Molecular dynamic simulation study of molten cesium

Molecular dynamics simulations were performed to study thermodynamics and structural properties of expanded caesium fluid. Internal pressure, radial distribution functions (RDFs), coordination numbers and diffusion coefficients have been calculated at temperature range 700–1600 K and pressure range 100–800 bar. We used the internal pressure to predict the metal–non-metal transition occurrence region. RDFs were calculated at wide ranges of temperature and pressure. The coordination numbers decrease and positions of the first peak of RDFs slightly increase as the temperature increases and pressure decreases. The calculated self-diffusion coefficients at various temperatures and pressures show no distinct boundary between Cs metallic fluid and its expanded fluid where it continuously increases with temperature

Molecular simulations of adsorption and separation of ethylene/ethane and propylene/propane mixtures on Ni₂(dobdc) and Ni₂(m-dobdc) metal-organic frameworks

<p>Porous solid adsorbents have received considerable attention as a promising alternative to the traditional cryogenic distillation for separating olefin/paraffin mixtures. In this work, we studied pure components as well as ethylene/ethane and propylene/propane binary mixtures uptakes and selectivities at 318 K and 1 bar into metal-organic frameworks Ni₂(dobdc) and Ni₂(m-dobdc) using GCMC simulations. We used DFT method to modify the potential model of carbon–carbon double bond in unsaturated hydrocarbons. GCMC results show that ethylene and ethane uptakes on Ni₂(m-dobdc) are higher than that of Ni₂(dobdc) but propylene and propane uptakes are equal in Ni₂(m-dobdc) and Ni₂(dobdc). Also, Ni₂(m-dobdc) has higher selectivity than Ni₂(dobdc) for separation of ethylene/ethane and propylene/propane mixtures.</p

A theoretical investigation on the regioselectivity of the intramolecular hetero Diels-Alder and 1,3-dipolar cycloaddition of 2-vinyloxybenzaldehyde derivatives

The present study reports a systematic computational analysis of the two possible pathways, fused and bridged, for an intramolecular hetero Diels-Alder (IMHDA) and an intramolecular 1,3-dipolar cycloaddition (IMDCA) of 2-vinyloxybenzaldehyde derivatives. The potential energy surface analysis for both reactions is in agreement with experimental observations. The activation energies associated with the two regioisomeric channels in IMHDA reaction show that the bridged product is favored, although in IMDCA, the most stable TS results the fused product. The global electronic properties of fragments within each molecule were studied to discuss the reactivity patterns and charge transfer direction in the intramolecular processes. The asynchronicity of the bond formation and aromaticity of the optimized TSs in the Diels-Alder reaction as well as cycloaddition reaction were evaluated. Finally, 1H NMR chemical shifts of the possible regioisomers have been calculated using the GIAO method which of the most stable products are in agreement with the experimental data in the both reaction